In women, the prevalence of cardiovascular diseases (CVD), particularly coronary heart disease (CHD) and cerebrovascular disease, increases markedly after menopause. An increased prevalence of hypertension is the primary factor contributing to this rise in CVD. Stage 1 ("mild") essential hypertension, both diastolic hypertension (diastolic arterial blood pressure [DBP] 90-99 mmHg with either normal or elevated systolic arterial blood pressure [SBP]) and isolated systolic hypertension (ISH -- SBP l40-159 mmHg with normal DBP), accounts for most of the increase in BP-related CVD risk. Adverse changes in other (i.e., non-BP) risk factors for CHD also contribute to the increased prevalence of CVD in postmenopausal women. As such, several health organizations have stated that any anti-hypertensive therapy should also, if possible, improve these other CHD risks factors. Regular aerobic exercise lowers BP in some hypertensive populations, but its efficacy for reducing BP and improving other CHD risk factors in postmenopausal women with either diastolic hypertension or ISH is unknown. Accordingly, the present study will determine: (Specific Aim 1) if regular aerobic exercise lowers BP at rest in postmenopausal women with Stage I essential hypertension compared to an active treatment control (i.e, moderate dietary sodium [Na] restriction); (Specific Aim 2) if the magnitudes of the reductions in BP in response to regular exercise are similar in postmenopausal women with diastolic hypertension vs. those with ISH; and (Specific Aim 3) if regular aerobic exercise also can improve other risk factors for CHD in this population. To achieve these aims, over a 5-year study period, 200 otherwise healthy postmenopausal women with Stage 1 essential hypertension (100 with diastolic hypertension and 100 with ISH) will undergo extensive screening and baseline measurements followed by random assignment to a 26-week period of either aerobic exercise intervention (moderate-intensity walking) or active treatment control (dietary Na restriction). BP at rest, aerobic exercise capacity, compliance to the exercise intervention (or control), and other CHD risk factors will be measured during and/or after the 26-week periods. Systemic hemodynamic, autonomic, neurohumoral, and structural determinants of BP also will be examined to gain insight into the mechanisms by which exercise lowers BP in these women.